technical reference
313
Synrad
Series 48Series 48
Series 48Series 48
Series 48 operator’s manual
Controlling laser power
Users who intend to use a gating signal should set the UC-2000’s gate input logic to internal pull-down
(normally off) mode. This prevents the beam from being enabled unless a TTL logic high (+3.5 V to 5.0
VDC) signal is applied to the Gate input connector. In the pull-down (normally off) mode an asserted
logic low state, short circuit to ground, or an open or disconnected Gate input locks the beam off.
See the UC-2000 Laser Controller Operator’s Manual for further information on setting up the UC-2000
Controller to gate the laser.
Many CO
2
lasers operating in applications requiring short gating pulses at repetition rates below 500 Hz
will exhibit some leading edge overshoot regardless of the PWM frequency. This occurs because a cooler
lasing medium (the CO
2
gas) is more efficient than a hotter one. This overshoot is more pronounced at
lower gating frequencies since the gas has a longer time to cool down between Command signal pulses.
Marking/engraving operation
When the delay between the end of one PWM Command signal pulse and the beginning of the next
PWM pulse exceeds 200 µs (less than or equal to 5 kHz), the UC-2000 Controller or FH Series marking
head sends a tickle pulse to maintain plasma ionization in the tube. Because the Controller can not
anticipate when the next PWM Command pulse will arrive, the tickle pulse can effectively merge with a
PWM signal that follows closely afterwards. When the PWM pulse that follows is short, causing the
tickle pulse to become a significant fraction of the PWM pulse duration, then the tickle pulse effectively
substantially increases the length of the PWM pulse it has merged with. For subtle marking applications
on sensitive, low threshold materials this lengthened PWM pulse may affect mark quality.
While this situation can occur when using PWM Command signal frequencies of 5 kHz and less, it is
important to note that it isn’t the Command signal frequency itself that is the determining factor but
rather this behavior happens only when the off time between PWM pulses exceeds 200 µs.
Warning
serious
personal
injury
The UC-2000’s default factory gate logic is set to internal Pull-Up
(normally on) mode. A TTL high input signal OR an open (discon-
nected) gate connector will cause the beam to turn on. To gate the
beam off, apply a logic low input, short circuit the Gate input
connector, or reconfigure the Controller to Gate Pull-Down
(normally off) operation.
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